The present invention relates generally to a method of coating tubular structures using a self-assembly process, and more specifically to a method of forming thin film coatings on inner surfaces of tubular structures.
Thin film coatings comprising micro- and/or nanoscale particles are of technological interest. Such coatings can impart coated substrates new attributes and functionalities, including chemical, optical and electronic properties as well as surface texture. Example applications of such coated substrates include photonic crystals, small lasers formed in 2-D assembly of colloidal particles, films for tailoring surface conductivity on composite substrates for sensor applications, waveguides, coatings for modification of rheological properties, surface-enhanced Raman scattering (SERS) substrates, etc.
A variety of different methods for assembling micro- and/or nanoscale particles into thin film coatings on solid substrates are known. For example, thin film coatings can be formed by adsorption onto a substrate from a solution driven by chemical affinity, by electrostatic attraction (e.g., layer-by-layer or LBL deposition), or by an electrical field (electrophoretic deposition), evaporation-induced self-assembly, convective assembly, dip coating, spin coating, gravitational sedimentation, self-assembly under confinement, assembly at an air-liquid interface using, for example, a Langmuir-Blodgett technique, assembly at a liquid-liquid interface, etc. However, most of these methods are limited in practical applications by small sample sizes, slow coating rates, difficulty in controlling coating thickness, and/or the need for complex equipment.
In addition to the above-mentioned shortcomings, most known methods are generally limited to thin film formation on a flat plate or outer surface of a tube or fiber. In view of the foregoing, it would be advantageous to provide a thin film coating method that addresses some or all of the limitations mentioned above, but particularly the ability to form thin film coatings in confined spaces, such as on the inside of tubes or other enclosed structures.
These and other aspects and advantages of the invention can be achieved by a self-assembly method for forming a thin film coating. The method includes immersing a tubular workpiece onto which the coating is to be provided lengthwise into a liquid subphase, inserting a first end of a delivery tube into the tubular workpiece so as to bring a distal end surface of the delivery tube to within a predetermined distance from the liquid surface, dispensing a liquid suspension of coating particles into the delivery tube to form a monolayer of the coating particles on the liquid surface in an area of the liquid surface between an inner surface of the tubular workpiece and an outer surface of the delivery tube, and withdrawing the tubular workpiece from the liquid subphase. During the withdrawing, the monolayer coating of coating particles formed on the liquid surface is transferred to the workpiece to form a coating of the coating particles on the inner surface thereof According to embodiments, the coating particles comprise nanoscale or larger particles.
Additional features and advantages of the invention will be set forth in the detailed description which follows, and in part will be readily apparent to those skilled in the art from that description or recognized by practicing the invention as described herein, including the detailed description which follows, the claims, as well as the appended drawings.
It is to be understood that both the foregoing general description and the following detailed description present embodiments of the invention, and are intended to provide an overview or framework for understanding the nature and character of the invention as it is claimed. The accompanying drawings are included to provide a further understanding of the invention, and are incorporated into and constitute a part of this specification. The drawings illustrate various embodiments of the invention and together with the description serve to explain the principles and operations of the invention.